The present invention relates generally to a method of detecting the presence of an insult in an absorbent article while it is being worn by a wearer.
Disposable absorbent articles find widespread use as personal care products such as diapers, children's toilet training pants and other infant and child care products, adult incontinence garments and other adult care products, sanitary napkins and other feminine care products and the like, as well as surgical bandages and sponges and medical garments. These articles absorb and contain body waste and are intended to be discarded after a limited period of use; i.e., the articles are not intended to be laundered or otherwise restored for reuse. Conventional disposable absorbent articles comprise an absorbent body disposed between an inner layer adapted for contacting the wearer's skin and an outer layer for inhibiting liquid waste absorbed by the absorbent body from leaking out of the article. The inner layer of the absorbent article is typically liquid permeable to permit body waste to pass therethrough for absorption by the absorbent body.
Disposable absorbent training pants, in particular, are useful in toilet training children. Typically, these disposable undergarments are similar to washable, cloth underwear in the manner in which they are put on and worn, yet provide an absorbent function similar to diapers to maintain skin health. Training pants provide a child undergoing toilet training with an undergarment that eases the transition from diapers to washable, cloth underwear as they become more confident in their ability to use the toilet independently.
In order to learn to use the toilet independently, a child must first learn to recognize when urination has occurred. Because urination may often occur during an activity that distracts the child to the extent that the child does not notice urination, this recognition can represent a substantial hurdle in the training process. Also, a child's ability to recognize when urination occurs may be hampered by the improved performance of disposable absorbent undergarments which quickly draw and retain urine away from the wearer's skin after an insult occurs.
Close monitoring of a toilet-training child by a caregiver can be helpful in that when urination occurs it can be discussed by the child and caregiver to enhance and improve the learning experience. Therefore, it is beneficial to provide the caregiver with immediate notification and/or verification that urination has occurred so that it may be discussed with the child while the event is still fresh in the child's mind.
One way of monitoring a toilet-training child is by using a system that detects a change in an electrical property of the undergarment which electrical property is a function of the wetness of the undergarment. For example, the electrical property may be resistance, conductance, impedance, capacitance or any other parameter which varies as the wetness of the undergarment varies. For example, pair of spaced apart parallel conductors may be situated within the absorbent material of the undergarment. These conductors are in electrical contact with the absorbent material of the undergarment and are connected to a sensing circuit for monitoring the electrical property, the circuit includes a power source, such as a battery. For example, the circuit may comprise a voltage divider for detecting resistance between the conductors. The output of the circuit is an analog output voltage that corresponds to a resistance value. When the undergarment is dry, the resistance between the conductors is extremely high and relatively infinite, appearing as an open circuit. When the undergarment is wet, more particularly when the absorbent material of the undergarment between the conductors becomes wet, the resistance of the undergarment at that area drops to a relatively lower value because urine acts as a conductor.
Accordingly, in a conventional system a sensor monitors the resistance between the conductors and compares resistance values to a predetermined and fixed threshold resistance value. If a resistance value is less than the threshold resistance value, then the sensing circuit (herein sensor) sends a signal to an alarm device, which informs the caregiver and/or the wearer that the wearer has urinated. For example, the alarm device may be a device for producing an auditory signal, such as a song, a visual signal, such as a light, or a tactile signal, such as a change in temperature.
These conventional devices may be prone to giving false positives, that is informing the caregiver and/or the user that there is urination present in the undergarment when there is not because there is only one “check” or “test” for the presence of urination (i.e., whether the resistance of the undergarment falls below a fixed threshold value). There are situations, such as when the child sits or other pressure is applied to an undergarment that has been previously insulted, when the resistance of the undergarment may fall below the threshold value, thus indicating a new insult, when in fact a subsequent insult has not occurred (i.e., detecting a false-positive). Accordingly, conventional devices may be ill-suited for accurately detecting multiple insults and/or preventing the detection of false-positives. Moreover, sweat may at least somewhat saturate the undergarment, typically over a relative lengthy period of time, and may trigger the sensor. Moreover still, after a first insult of urination by the wearer, the resistance value of the undergarment is substantially less than when the product was dry. However, the threshold value has not changed, and therefore, the resistance may be lower than the threshold, thus triggering an alarm, even though a subsequent insult has not occurred.